Optical fibre splice enclosures

Abstract: An enclosure assembly for optical fibre splices or other optical fibre components comprises a plurality of trays (20) disposed in a stack with the trays inclined at a common angle to a longitudinal axis of the stack. Each tray is of generally elliptical shape in plan and is pivotally mounted, adjacent one end of its major axis, to an elongate support (10).

Description: This invention relates to an enclosure assembly for optical fibre splices or other optical fibre components, the assembly comprising a plurality of trays each tray being mounted by an edge thereof to an elongate support and disposed in a stack with the trays inclined at a common angle to a longitudinal axis of the stack. WO91/06024 discloses an enclosure assembly of the above-mentioned type. It is often desirable for such enclosure assemblies to occupy minimum space, yet the fibres entering and leaving the assembly must not be bent to radii smaller than a predetermined minimum. In accordance with this invention there is provided an enclosure assembly of the above-mentioned type, which is characterised in that each tray is of generally elliptical shape in plan and is pivotally mounted, adjacent one end of its major axis, to the elongate support. Because the elliptical trays are longer in one dimension than if they were circular, they can accommodate splices or other components of relatively long length, as becomes necessary if the overall size of the enclosure and its trays has to be reduced. However, the elliptical trays still project a generally circular "footprint", so that the stack of trays fits closely within a cylindrical cover when applied over the stack. Preferably each tray has at least one opening formed in its floor and open to its periphery, enabling fibres to pass from one tray to the next tray along a circumferential path. Preferably this opening in each tray is adjacent its point of pivotal mounting to the elongate support: then the adjacent trays can be pivoted away from each other, or they can be pivoted together, without stressing the fibres passing between the trays. Preferably each tray has at least one fibre entry adjacent its point of pivotal mounting to the elongate support, and also at least one fibre entry adjacent its opposite end. Preferably the enclosure enables the trays to rest in a downwardly inclined orientation, but enables the trays to be held, alternatively, in an upwardly inclined orientation: in the first case fibres may enter the trays from their outer or front ends, and in the second case the fibres may instead enter the trays from their pivoted or rear ends. Preferably each tray has at least one opening formed in its floor through which a fibre runs in passing from one tray to the next. The assembly may be formed as a module which comprises a tubular housing which contains the stack of trays. Embodiments of this invention will now be described by way of examples only and with reference to the accompanying drawings, in which: FIGURE 1 is a side elevation, partly in section, of an enclosure assembly in accordance with this invention, shown with its tubular cover removed; and FIGURE 2 is a plan view of one of the trays used in the assembly of Figure 1. Figure 1 shows the internal components of an enclosure assembly for optical fibre splices. A backbone 10, in the form of a rectangular-section strip of metal, projects upwards from a base 12 which is formed with a number of tubular cable entry ports 14 projecting from its underside. A plurality of trays 20 are pivotally coupled to the backbone 10, in that each tray is formed with an aperture 21 adjacent its edge, through which the backbone extends. A stop 18 is mounted to the top of the backbone 10, and projects from the backbone in a forwards direction, and also in an inclined upwards direction of e.g. 55° to the horizontal. An abutment member 9 is slidably mounted on the backbone 10 at its lower end, and is lightly urged upwards and against the stack of trays 20, by a spring 8: the abutment member 9 has an inclined top surface and the stack of trays are able to rest partly on this and partly on an inclined portion 11 of the backbone, the trays then resting at a downwardly inclined angle of e.g. 55°. It will be appreciated therefore that the trays can be pivoted through up to 110° between a downwardly inclined position (shown for the bottom few trays) and an upwardly inclined position (shown for the top few trays). The enclosure is completed by a cylindrical cover member (not shown) which is closed at its upper end and can be placed over the assembly of pivotally mounted trays, for its open bottom end to sit on the base 12. Figure 2 shows one of the trays 20 in detail. Thus, each tray is of generally elliptical shape in plan view and has a flat floor 26 and an upstanding peripheral wall 22. A projection 23 at one end (the rear end) of the tray is formed with the aperture 21 which serves for pivotally mounting the tray to the backbone 10 of the enclosure. A slot 23a is provided to enable the tray to be engaged and disengaged with the backbone 10 by a sideways movement. Adjacent its opposite end (forward end), the peripheral wall is formed to provide two tangential fibre entries 24, one either side of the major axis of the tray: at the rear end of the tray, the peripheral wall is similarly formed with two tangential fibre entries 25. Also adjacent the rear end of the tray, the floor 26 of the tray is formed with two elongate windows 27, one either side of the major axis of the tray and each immediately adjacent the peripheral wall: further, the peripheral wall is formed with an aperture 28 to provide a free opening into each window 27. It will be noted that each window 27 is initially closed by an element 27, which also includes a tab 28a closing the wall opening 28: each element 27a is frangibly connected to the tray floor 26 and can be broken away when required, as shown. Optical fibres can enter or leave the tray through any of the tangential entries 24,25, or through the windows 27, as will be described below. However, Figure 2 shows fibres contained within flexible tubes 24a and 25a passing into the entries 24 and 25: any such fibres or tubes may be held by ties passed around them and through holes 26a in the tray floor. Within the tray, the optical fibres follow curved paths adjacent the peripheral wall 22: the floor of the tray is formed with ramp-section projecting lugs e.g. 29 spaced inwardly from the peripheral wall, to inhibit the fibres moving radially inwards. An elongate tab 30 projects radially inwardly from the top of the peripheral wall 22 and parallel to the tray floor, at the front end of the tray, and a similar tab 31 projects up from the floor and then radially outwards towards the rear end of the tray: the optical fibres run underneath these tabs and are prevented by these tabs from lifting out of the open top of the tray. Two sets of parallel ribs 34 are formed on the floor of the tray, these two sets of ribs being spaced-apart along the minor axis of the tray and symmetrically-positioned either side of the major axis of the tray: the ribs run parallel to the major axis of the tray, and serve to retain optical fibre splices or other components when inserted between adjacent such ribs. Each set of ribs is formed on a portion 35 of the floor, this portion being frangibly connected to the remainder of the floor. Thus, and as shown, each of these portions 35 can be broken away to leave an open window 36 (rectangular in shape in the example shown). A replacement pad 37 may be snap-fitted into this window, the replacement pad 37 being formed with a fewer number of wider-spaced ribs, to retain splices or other components of wider dimensions. It will be appreciated that because the tray 20 is generally elliptical, it can accommodate longer splices (or other components) at the designated positions, than if the tray were circular. However, when the stack of trays are disposed in an inclined rest position as shown in Figure 1, they project a generally circular "footprint" onto the base 12: accordingly, the stack of trays fit closely within a circular-section tubular cover, when the latter is fitted. The windows 27 in the floor 26 of each tray 20 enable fibres to pass directly from one tray to the next tray of the stack. Thus, one or more fibres may, after following their curved path within one tray, simply pass up through a window 27 of the next tray above, and follow the usual curved path within that next tray: in passing from one tray to the next, the fibre or fibres simply continue to follow their usual curved path without any significant change of direction. It will be appreciated that because of the positions of the windows 27 adjacent the pivotal mounting of the trays 20 to the backbone 10, the trays can still be pivoted relative to the backbone, without applying any significant stress to any optical fibres which run from one tray to the next via the windows 27: such a fibre is shown at F in Figure 2. It will further be appreciated that the openings 28 in the peripheral wall 22 enable optical fibres to be inserted into the windows 27 by a simple sideways movement of the fibres. A particular use of the windows is where a fibre enters a first tray and passes to a splitter in that tray, then the two (or more) fibres from that splitter pass to a second tray in the stack, where they are spliced to a corresponding number of fibres which then pass to a corresponding number of splitters in a third tray, and so on. Thus through a succession of trays in a stack, a single fibre entering a first tray can be split into a large number of outgoing fibres. Instead of housing splitters, the alternate trays may house combiners, so that a plurality of incoming fibres may be combined into a single outgoing fibre.

Claims: An enclosure assembly for optical fibre splices or other optical fibre components, the assembly comprising a plurality of trays (20) each tray being mounted by an edge thereof to an elongate support (10) and disposed in a stack with the trays (20) inclined at a common angle to a longitudinal axis of the stack, characterised in that each tray (20) is of generally elliptical shape in plan and is pivotally mounted, adjacent one end of its major axis, to the elongate support (10). An enclosure assembly as claimed in claim 1, wherein each tray (20) has one or more openings (27) formed in its floor (26) and open to its periphery, to enable one or more optical fibres to pass from one tray (20) to the adjacent tray (20) along a curved path extending between the respective peripheries of the trays (20), with each end of the path being tangential to its corresponding tray (20). An enclosure assembly as claimed in claim 2, wherein said opening or openings (27) are positioned adjacent the pivotal mounting of the tray (20) to said support (10). An enclosure assembly as claimed in claim 2 or 3, wherein the floor of the tray (20) comprises a frangibly connected element (27a), which can be removed to form a said opening (27). An enclosure assembly as claimed in any preceding claim, wherein each tray (20) has a peripheral wall (22), which is generally orthogonal to the floor (26) of the tray (20), and which is formed with one or more fibre entries (24,25) adjacent said one end of its major axis and/or adjacent the opposite end of its major axis. An enclosure assembly as claimed in any preceding claim, wherein each tray has at least one portion (35) of its floor (26) provided with means (34) for retaining optical fibre splices or other optical fibre components, the or each said portion (35) being frangibly connected to said floor (26) and replaceable by a similar portion (37) having alternative retaining means.

Inventors: CAMMACK ANDREW STEPHEN, FOSS RAYMOND CHARLES, CAMMACK,ANDREW STEPHEN, FOSS,RAYMOND CHARLES
Applicants: BOWTHORPE PLC
Application year: 1994
Main classification: G02B6
IPC codes: G02B6